As civil society organizations from around the world, we write to you to respectfully put forward our views on the issue of the release of genetically modified (GM) Aedes aegypti mosquitoes in Malaysia. It is not clear when such releases will occur, but given the tremendous international interest in the issue, it would be regrettable if the field trials were to be shrouded in secrecy.

We are equally concerned by news of the field releases in 2009 and 2010 of the same GM mosquitoes in the Cayman Islands and are calling for a transparent assessment of the health and environmental impacts of these trials, pending which, no further field releases of GM mosquitoes should occur. The Cayman trials have also been strongly criticized for being conducted without public consultation or ethical oversight and for not seeking the informed consent from local people.

While we appreciate that dengue is a serious problem in Malaysia and that urgent measures are needed to address this debilitating disease, the release of GM mosquitoes presents a unique moment in the history of the application of genetic engineering technology, which is of international significance. We know that the government of Malaysia has not taken this decision lightly, and appreciate the efforts that have been made to responsibly assess the technology and the risks associated with the release of these GM mosquitoes into the environment. However, there are several outstanding issues that would benefit from a more cautious approach.

Scientific uncertainties call for a precautionary approach

GM mosquitoes are a very new application of GM technology and present very different risks, and for which the international community has had virtually no risk assessment or regulatory experience.

Unintended and unpredictable changes may occur (often not instantly noticeable), and a focus on testing for these effects in the laboratory should be the first step, rather than testing fitness parameters in the open environment, as appears to be the intention of these field trials. Further, the interactions in the wild between the two dengue-carrying mosquito species, their predators and prey, the evolution of the diseases that they carry, and the human population, should be better understood before introducing technologies of this kind in open field release. This requires more sophisticated computer modelling, informed by a better ecological baseline of unmodified mosquitoes in the wild.

It would be therefore prudent to ensure that any questions remaining should be first investigated. As such, the Precautionary Principle dictates that it is still too early for any open field releases, especially given the fact that there will be GM mosquitoes, including females which potentially transmit disease, surviving in the environment due to the known 'leakiness' of the technology employed (around three percent in the published literature). Of particular concern is whether the survival rates in subsequent generations will eventually select for mosquitoes that can overcome the conditional lethality trait. Survival of the GM larvae also means that the transgenes may not be completely removed from the environment, with possibly hazardous consequences.

Pitfalls of a GM mosquito strategy for dengue control

If the world is to approach dengue control using GM mosquitoes, we may be locking ourselves onto a 'genetic treadmill' that would be difficult to reverse. At the commercial release stage, the continuous release of millions of GM mosquitoes at several places would be needed in order to successfully suppress target mosquito populations. In such large numbers the concerns raised over the field trials would be magnified many times over, plus would raise other additional risks.

From the public health perspective, of particular concern is whether population suppression of Aedes aegypti (which is the ultimate aim of these GM mosquitoes) would lead to other closely related and disease-transmitting species, such as Aedes albopictus, filling the vacated niche and hence continue to cause, or even worsen, the dengue problem, or transmission of other serious diseases.

The company that produces and owns the GM Aedes aegypti mosquitoes, UK-based Oxitec Limited, is also developing a similar GM Aedes albopictus mosquito, presumably in anticipation of this problem. Oxitec clearly stands to gain from the approval of its products in countries such as Malaysia. However, it is unclear who will bear the liability and from whom victims should seek redress, should any damage to the environment or human health or animal health occur.

Right to health and participation are priorities

Instead of a dengue control strategy beholden to private and vested interests, the participation of people and peoples' organizations is essential to, and would benefit the formulation, implementation and evaluation of all health policies and programmes. We respectfully urge the Malaysian government to ensure meaningful and effective public participation on this matter, as it is committed to under its Biosafety Act 2007 and as a Party to the Cartagena Protocol on Biosafety. There is also a need to put in place a serious and proper prior informed consent regime, especially considering that the whole world will be looking to the Malaysian experience as a model.

Human well-being is at the core of public health and governments have a duty to respect, protect and fulfil peoples' right to health, as well as refrain from taking actions that can jeopardize the right to health of its citizens. We therefore respectfully urge the Malaysian government to reconsider the decision to allow field experiments of the GM mosquitoes, not only for the benefit of Malaysians, but also for the world at large.